Different types of levelling spacer devices for laying slab products for cladding laying surfaces are known in the art.
Specifically, among others, EP2565346B1 discloses a levelling spacer device including the features of the preamble of claim 1 of the present invention, i.e.:                a support comprising a base, positionable on the backside of a laying surface of at least two slab products that are adjacent and flanked with respect to a flanking direction, and at least a separator element projecting from said base and configured and arranged to contact at least a portion of facing flanks of the two slab products, said separator element being provided with a through-window with an upper edge destined to be located superiorly of the level of an in-view surface of the slab products and a lower edge destined to be located inferiorly of the level of said in-view surface of the slab products; and        a presser wedge configured and arranged to be inserted in the through-window and to slide restingly on the in-view surface of the slab products, with an upper face cooperating with the upper edge of the through-window to push the slab products towards the base.        
Although the force exerted to push the slab products towards the base is enough for many applications, there are other applications for which a larger push force (and therefore a larger pressure, for the same area) is required in order to assure a more accurate leveling of adjacent slab products (for example when the amount of cement under adjacent slab products is not uniform) and/or for providing a stronger gluing of the slab products to the cladding laying surface.
It is, therefore, necessary to provide an alternative to the state of the art which covers the gaps found therein, by providing a levelling spacer device which really provides such a larger push force.